Satellite communication has long been used to broadcast data to computers. In situations requiring the same data to be transmitted to multiple sites, satellite communication, which allows a single transmission of data to be received at multiple sites, can be more cost effective than terrestrial communication, which requires separate transmission to each site.
In the past, data broadcast via satellite to a computer typically was received by an external satellite receiver, which serially passed a single data stream to the computer through a serial adapter interface. An example of such a system is the Opportunistic Data File Broadcast system developed by Hughes Network Systems, which employs a Compression Labs Spectrum Saver satellite receiver to pass RS-422 serial data to high-speed adapters in computers at remote sites. This particular system has been used by financial institutions to broadcast financial data from central data centers to branch offices.
For commercial data broadcasts, conditional access technology enabling only authorized users to access the broadcast data is essential to ensure payment for the data. Conditional access is typically implemented by encrypting the broadcast data and providing the decryption keys only to authorized receivers. In prior satellite data communication systems, such as the Opportunistic Data File Broadcast system, conditional access functions have been performed by the external satellite receiver, which outputs a single decrypted data stream to the receiving computer. In these systems, conditional access is provided for only a single data stream. Thus, to access multiple data streams simultaneously transmitted would require users to have a complete set of receiving equipment for each data stream.
Another type of satellite communication system has been suggested in which an adapter card, insertable into a computer, enables satellite reception without the need for the external satellite receiver. Examples of such systems are disclosed in U.S. Pat. No. 4,777,657 to Gillaspie, U.S. Pat. No. 5,019,910 to Filmer, and U.S. Pat. No. 5,359,367 to Stockill.
However, these references fail to teach a system incorporating conditional access technology, and similarly fail to provide for simultaneous receipt of multiple data streams where the data streams are individually conditional access controlled. Furthermore, to the extent that the prior art discloses use of decryption hardware, none of the prior art systems extends the use of the hardware beyond decrypting an incoming broadcast data stream to providing encryption and decryption operations for the connected computer.